1. Field of the Invention
The present invention relates to a color picture copying apparatus and a color copying method to be carried out by the color picture copying apparatus and, more specifically, to a color copying machine capable of finishing the surface of a color-printed recording sheet in either a glossy surface or a dull surface and of reproducing the colors of a document with excellent color reproduction, and a color copying method to be carried out by the color copying machine.
2. Discussion of the Related Art
The conventional color copying machine, such as disclosed in Japanese Patent Laid-open (Kokai) No. 57-101840, which corresponds to U.S. Pat. No. 4,458,265, or U.S. Pat No. 4,959,711, is provided with a color signal input unit for inputting color signals representing the colors of a document, such as a red signal R, a blue signal B and a green signal G which each correspond to a primary color. The color copying machine is further provided with a recording unit for recording the color picture of an original color picture on the basis of printer control signals for controlling a cyan printing by using a cyan ink C, a magenta printing by using a magenta ink M and an yellow printing by using an yellow ink Y. An arithmetic unit, which is connected to the color signal input unit and the recording unit, changes the color signals including the red signal R, the blue signal B and the green signal G into the printer control signals related to the cyan C, the magenta M and the yellow Y by using a matrix representation as represented by Expression (1) described below in conformity to a predetermined rule to produce cyan printer control signals, magenta printer control signals and yellow printer control signals.
The printer control signals define whether or not the cyan ink C, the magenta ink M and the yellow ink Y are to be applied to a recording sheet or define respective quantities of the inks to be applied to the recording sheet to record a color image on the recording sheet. ##EQU1## where R, G and B are input color signals representing the color picture of the original color picture, C, M and Y are printer control signals for controlling the cyan printing, the magenta printing and the yellow printing, and aij are coefficients for color modification.
When the document has a glossy surface like a photograph, it is desired that the surface of a printed recording sheet carrying the color picture copy of the original color picture be finished in a glossy surface. Therefore, a user uses a laminator to laminate a transparent lamination onto the recording sheet so that the surface of the printed recording sheet is finished in a glossy surface. On the other hand, when the document has a dull surface, it is not desired to finish the surface of the printed recording sheet with a glossy surface in most cases.
The glossy printed surface of a recording sheet has the effect of a virtual increase in photographic density and color saturation, because the glossy printed surface has a characteristic of increasing the ratio of regularly reflected light to the total light reflected in all directions. On the other hand, the dull surface has a characteristic of increasing the ratio of diffused light to the total light reflected in all directions. The effect of the dull surface is a virtual decrease in the photographic density of the color picture and color saturation.
The arithmetic unit of the conventional color copying machine has no function to modify the printer control signals according to the surface-finishing condition, that is, whether or not the recording sheet is glazed after recording the color picture thereon.
Accordingly, if the arithmetic unit is designed so as to produce printer control signals so that the colors of an original color picture are reproduced satisfactorily on a recording sheet which is not to be glazed, the photographic density and color saturation of the color picture recorded on the recording sheet will increase if the printed recording sheet is glazed which deteriorates the colors reproduced on the recording sheet.